title: The effect of consequent exposure of stress and dermal application of low doses of chlorpyrifos on the expression of glial fibrillary acidic protein in the hippocampus of adult mice.
abstract: BACKGROUND
  Chlorpyrifos (CPF), a commonly used pesticide worldwide, has been reported to produce neurobehavioural changes. Dermal exposure to CPF is common in industries and agriculture. This study estimates changes in glial fibrillary acidic protein (GFAP) expression in hippocampal regions and correlates with histomorphometry of neurons and serum cholinesterase levels following dermal exposure to low doses of CPF with or without swim stress.
  
  
  METHODS
  Male albino mice were separated into control, stress control and four treatment groups (n = 6). CPF was applied dermally over the tails under occlusive bandage (6 hours/day) at doses of 1/10th (CPF 0.1) and 1/5th dermal LD50 (CPF 0.2) for seven days. Consequent treatment of swim stress followed by CPF was also applied. Serum cholinesterase levels were estimated using spectroflurometric methods. Paraffin sections of the left hippocampal regions were stained with 0.2% thionin followed by the counting of neuronal density. Right hippocampal sections were treated with Dako Envision GFAP antibodies.
  
  
  RESULTS
  CPF application in 1/10th LD50 did not produce significant changes in serum cholinesterase levels and neuronal density, but increased GFAP expression significantly (p < 0.001). Swim stress with CPF 0.1 group did not show increase in astrocytic density compared to CPF 0.1 alone but decreased neuronal density.
  
  
  CONCLUSIONS
  Findings suggest GFAP expression is upregulated with dermal exposure to low dose of CPF. Stress combined with sub-toxic dermal CPF exposure can produce neurotoxicity.
authors.affiliation: Postgraduate & Research Department, International Medical University, No.126, Jalan 19/155B, Bukit Jalil, 57000, Kuala Lumpur, Malaysia.
authors.forename: Kian Loong
authors.initials: KL
authors.lastname: Lim
authors.affiliation: Pathology Department, International Medical University, No.126, Jalan 19/155B, Bukit Jalil, 57000, Kuala Lumpur, Malaysia.
authors.forename: Annie
authors.initials: A
authors.lastname: Tay
authors.affiliation: Human Biology Department, International Medical University, No.126, Jalan 19/155B, Bukit Jalil, 57000,Kuala Lumpur, Malaysia.
authors.forename: Vishna Devi
authors.initials: VD
authors.lastname: Nadarajah
authors.affiliation: Human Biology Department, International Medical University, No.126, Jalan 19/155B, Bukit Jalil, 57000,Kuala Lumpur, Malaysia.
authors.forename: Nilesh Kumar
authors.initials: NK
authors.lastname: Mitra